Panel and Use of Such a Panel As A Scaffolding Board or a Building Panel

ABSTRACT

The present invention relates to a panel comprising two parallel skin plates made of wood or a wood material, between which ribs extend for stiffening the panel, wherein the ribs are at least substantially made of wood or a wood material. The present invention further relates to the use of such a panel as a scaffolding board or a construction element and to scaffolding provided with such panels.

CLAIM OF PRIORITY

This application is a continuation-in-part of U.S. patent applicationSer. No. 12/247,607 filed Oct. 8, 2008, which claims priority toPCT/NL2007/000098 filed Apr. 12, 2007, the National Stage ofInternational Application No. PCT/NL2007/000098 filed Apr. 12, 2007.

FIELD OF THE INVENTION

The present invention relates to a panel comprising two parallel skinplates made of wood or a wood material, between which ribs extend forstiffening the panel.

DESCRIPTION OF RELATED ART

Such panels are known, they are used inter alia for doors in houses. Theskin plates are made of plywood and form the outer sides of the door.Present between the skin plates is a honeycomb structure of cardboard,which functions to stiffen the door. Such a panel is in itself suitablefor use with a door that separates two internal spaces of a buildingfrom each other, but it is less suitable for taking up comparativelylarge forces. Thicker skin plates, and in some cases even solid wood,are used for relatively heavy applications. In the case of doors, theskin plates are provided on a framework. In some cases the frameworkcomprises cross slats, which extend between circumferential edges of theframework. Said cross slats are not regarded as ribs in the presentdocument. Ribs can be distinguished from the framework in that they aremade of a different material and/or have a different thickness or otherproperties.

these prior art laminated panels do not provide the necessary stiffnessfor many applications for which an improved panel might find use, andaccordingly, an improved panel is believed to be necessary.

SUMMARY OF THE INVENTION

Consequently it is an object of the present invention to provide a panelas referred to in the introduction which is also suitable for heavierapplications, without thicker skin plates or skin plates of a strongertype of wood being absolutely required. This object is achieved by thepresent invention In that the ribs are at least substantially made ofwood or a wood material. By making the ribs of a material which is morerigid than the cardboard that has been used so far for the ribs, theribs are capable of taking up larger forces and it is possible to usethe panel for heavier applications, in other words, for taking upgreater loads, and thus take up heavier loads with a panel according tothe invention while using comparable skin plates. On the other hand itis possible to use less strong skin plates in comparison with the knownskin plates used in the panels according to the prior art for taking upcomparable forces, because the ribs will compensate the reducedstrength. With a number of applications it is even possible to use apanel according to the present invention instead of a solid plank.

In a preferred embodiment of the invention, the wood material comprisesmulti-ply or fibreboard. These materials make it possible to manufacturecomparatively strong skin plates from comparatively low-grade wood.Furthermore, fibreboard such as MDF or chipboard is a material intowhich wood waste can be incorporated, so that such materials can beregarded as environmentally friendly. The use of these wood materialsrelates both to the wood material for the skin plates and to the woodmaterial for the ribs.

In a preferred embodiment of the invention, the ribs are strip-shapedand extend crosswise from one of the two skin plates to the other skinplate, but for at least some embodiments, not into one or either of theskin plates. Strip-shaped ribs may simply be made of board materials andcan thus be produced separately from the skin plates, so that panels canbe assembled as desired at a relatively late stage.

In a preferred embodiment, at least some of the ribs extend parallel toeach other in their longitudinal direction. This leads to a uniformdistribution of the strength of the panel.

In a preferred embodiment of the invention. the spacing between twoadjacent ribs extending parallel to each other ranges between 1 and 10cm. This makes it possible to provide panels which on the one hand havesufficient/strength and which on the other hand are comparatively lightin weight.

Preferably, the ribs are arranged in a diamond-shaped and/or arectangular pattern. Such patterns further contribute to a uniformdistribution of the strength, or rigidity, of the panel.

In a preferred embodiment of the invention, intersecting ribs are eachprovided with a notch at the location of their points of intersection,with their notches engaging one another. In this way a diamond-shaped ora rectangular pattern can be readily formed whilst ensuring that the twosides of the strips make contact with the respective skin plates of thepanel, for many embodiments without extending into either of the twoskin plates. In addition, a kind of harmonica effect can be realized inthis manner, so that the shape of the system of ribs can be adapted to acertain extent before the ribs are provided between the skin plates.

The ribs preferably have a thickness of 0.5 to 2 mm. In this way theribs provide sufficient rigidly, whilst on the other hand the weight ofa panel according to the invention remains within bounds.

The ribs preferably have a width of 20 to 70 mm. The thickness of apanel is to a large extent determined by the width of the ribs and this,too, makes it possible to realize a wide range of panel thicknesses.

Preferably, the ribs are attached to the skin plates. As a result, theribs are fixed in position with respect to the planar skin plates,thereby ensuring a uniform support of the skin plates by the ribs,preferably without the ribs extending into the skin plates.

In a preferred embodiment of the Invention, the ribs are glued to theskin plates, preferably by means of a construction glue, furthermorepreferably by means of a water-resistant glue such as melamine glue.Gluing provides a strong connection between wood elements in a simplemanner. Water-resistant melamine glue is impervious to moisture, so thatthe panels can also be used in moist environments.

In another preferred embodiment of the invention. a fibre mat, a glassfibre mat in a preferred embodiment, is provided between the ribs andthe skin plates for stiffening purposes. Such fibre mats help todistribute the forces that are exerted on the skin plates over the ribs,so that a comparatively strong panel can be realized while usingcomparatively flexible materials for the skin plates.

In a preferred embodiment of the invention, the skin plates are providedon a framework. The framework may function both as a frame for definingthe outer circumference of the panel and for contributing to therigidity of the panel, in particular if part of the framework extendswithin the outer circumference of said frame, and thus of the panel.

The framework it is preferably made of wood. This reduces the number ofmaterials that are used with such a panel.

In a preferred embodiment of the Invention, the ribs are spaced from theframework. Since the dimension of the ribs is smaller than the distancethey must bridge between parts of the framework at the location inquestion, the ribs fit comparatively easily within the framework, whichfacilitates the assembly of the panel.

In a preferred embodiment of the invention, at least part of the panelhas been treated with a water-repellent material. This makes it possibleto use the panel in moist or even wet conditions, especially if awater-resistant glue is used in the case of the ribs being glued inplace.

In a preferred embodiment of the invention, the panel has a length of atleast 4 m and a width of at least 25 cm. Such a combination ofdimensions renders the panel suitable for use as a bearing element Inscaffolding, because of the advantageous stiffness/weight ratio of sucha bearing element and because of the favorable ratio of length to width,which as such corresponds to that of conventional scaffolding planks.Especially an embodiment in which the skin plates are fixed to aframework having such dimensions, in which the ribs are moreover affixedto the skin plates by means of a water-resistant construction glue, andin which the panel has been treated with a water-repellent material, isquite suitable for use in scaffolding.

The present invention further relates to the use of a panel as describedin the preceding paragraphs as a bearing element for use in scaffolding.Panels according to the present invention are very suitable for beingused as substitutes for scaffolding planks. Scaffolding planks aretraditionally made of solid wood, because they need to be strong (rigid)enough to support persons, tools and building materials, such as bricks,mortar and the like. A drawback of solid planks is that they arecomparatively heavy. The increasingly stringent safety, health andwelfare legislation imposes further and further limitations as regardsthe maximum load a worker is allowed to carry. Because of this. thescaffolding planks must be made lighter or be carried by two persons.Making the planks lighter can be realized by reducing their size, butthis has a cost-increasing effect because more operations need to becarried out for covering a comparable area when smaller planks are used.Apart from said legislation. the current scaffolding planks aredifficult to handle because the planks often need to be moved invertical direction. Finally, falling scaffolding planks, a situationwhich unfortunately happens rather frequently, lead to dangeroussituations, as such a heavy scaffolding plank may cause serious, in somecases even fatal injury when it hits a person.

A panel according to the present invention is intended for use as abearing element for use in scaffolding, which bearing element is lighterthan the traditionally used scaffolding planks and which moreover hasthe required constructional qualities. Depending on the selection ofwood or wood material, the construction with the wooden ribs between thewooden skin plates on the one hand provides sufficient strength to meetthe requirements made of a bearing element for use in scaffolding,whilst on the other hand a considerable saving in weight is achieved incomparison with scaffolding planks. Another advantage is that up to 70%less wood can be used in comparison with traditional scaffolding planks.If the embodiment of the panel that is used has been treated with awater-repellent material is used. the scaffolding board will certainlybe resistant to precipitation. The embodiment comprising a fibre matprovides an even stronger scaffolding plank or makes it possible torealize an even greater saving on wood.

The present Invention further relates to scaffolding comprising a frameof interconnected standards and ledgers and wooden bearing elementssupported on ledgers for supporting persons and/or building materials.Such scaffolding is known in the construction industry, they make use ofbearing elements in the form of solid scaffolding planks. The drawbackof using solid scaffolding planks has already been discussed In theforegoing, and consequently it is an object of the present invention toprovide scaffolding in which the drawbacks of the use of solidscaffolding planks are at least partially overcome. This object isachieved by the present invention in that the bearing elements comprisepanels according to the present invention. An important advantage ofthis is that the panels are easier to handle because of theircomparatively low weight. A further advantage is that the overallconstruction of the scaffolding will be less heavy in comparison withtraditional scaffolding that uses solid scaffolding planks as thebearing elements. In this way the risk of collapsing as a result of theframe being overloaded is significantly reduced, or a lighter frame canbe used for constructing the scaffolding.

The present invention also relates to a method for constructingscaffolding, comprising the steps a) constructing a frame ofinterconnected standards and ledgers and b) placing wooden bearingelements on the ledgers. Such a method is generally known in theconstruction industry. Frequently a sublevel of the frame isconstructed. after which bearing elements are provided, on which personsinvolved in the further erection of the scaffolding can subsequentlyposition themselves. The solid scaffolding planks that have been used asbearing elements so far are comparatively heavy, and frequently thescaffolding planks are lifted by hand. As a result of the increasinglystringent safety, health and welfare legislation, equipment is sometimesused for lifting the scaffolding planks, or shorter scaffolding planksare used, so that the work can still be carried out by hand. In bothcases, however, the efficiency with which the work is carried out isseriously diminished.

Consequently it is an object of the present invention to provide amethod as described in the preceding paragraph wherein the efficiency ofthe method can be maintained or even improved whilst complying with morestringent safety, health and welfare legislation. This object isachieved by the present invention in that in step b) panels according tothe present invention are placed on the ledgers as bearing elements.Step b) can be carried out after step a) has been completed, but inpractice steps a) and b) are often carried out iteratively forincreasing the height of scaffolding in steps. The advantage of usingpanels according to the present invention as bearing elements is thatcomparatively lightweight bearing elements are easier to handle than thescaffolding planks that have been used so far. As a result, the workinvolved in erecting scaffolding will be less heavy, whilst in additioncomparatively large panels may be used without acting in violation ofthe health and safety laws.

The present invention further relates to the use of a panel according tothe invention as a construction element. Many types and embodiments ofconstruction elements are known. By using a panel according to thepresent invention, comparatively lightweight construction elementsexhibiting a comparatively high degree of rigidity are provided, andcomparatively low-grade wood types may be used, whilst a requiredrigidity of the construction element is nevertheless realized.Construction elements in the form of panels according to the inventionmay be used as substitutes for planks and other panels in varioussectors, for example the construction industry and the furnitureindustry.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will be explained in more detail below on thebasis of a few preferred embodiments of the present invention. In thedescription, reference will be made to the appended drawings, in which:

FIGS. 1 a is a cutaway plan view of a panel according to the presentinvention;

FIG. 1 b is a cross-sectional view taken along the line A-A of FIG. 1 a.

FIG. 2 a schematically shows the manner in which the ribs of a preferredembodiment of the invention may be arranged relative to each other;

FIG. 2 b is an exploded view of the skin plates and ribs of a panelaccording to the present invention; and

FIG. 2 c is a perspective view of a panel according to the invention, inwhich a part of the upper skin plates has been left out for easyreference.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1 a, a plan view is shown of a panel 1 according tothe present invention, whose upper skin plate and associated fibre mathave been left out in the drawing. The panel 1 comprises a woodenframework 2 of relatively thick slats, within which ribs made of MDFextend in the longitudinal direction and in the transverse direction ofthe panel 1. Between the ribs, the bottom side of the panel 1 can bedistinguished, in this case a glass fibre mat 4 provided on a lower skinplate (not shown in FIG. 1 a).

FIG. 1 b shows a cross-sectional view of the panel 1 of FIG. 1 a, alongthe line A-A, in which ribs 3 extending in the longitudinal directionare present between the wooden framework 2 and skin plates 5, which areprovided with a fibre mat on the inner side of the panel.

FIGS. 2 a, 2 b and 2 c show another embodiment according to theinvention of a panel 11, in which ribs 13 extend between two skin plates15, which ribs jointly form a pattern of squares.

Referring now to FIGS. 1 a and 1 b, a panel 1 is shown which iscomparatively long and narrow and which is thus quite suitable for useas a scaffolding element. In FIG. 1 a an upper skin plate 5 and theupper glass fibre mat 4 have been removed. thus providing a view of theinterior of the panel for easy reference. A wooden framework 2 of planksor beams defines the outer circumference of the panel. As is shown inFIG. 1 b, two skin plates 5 are provided on either side of the framework2, and a glass fibre mat 4 is present on the inwardly facing sides ofthe skin plates 5. Said glass fibre mat 4 provides a more uniformdistribution of forces on the MDF ribs 3 in the panel, especially whencomparatively low-grade wood material is used for the skin plates 5. TheMDF ribs 3 extend in the longitudinal direction and in the transversedirection, forming a grid for distributing the forces that are exertedon a skin plate 5, so that the panel will behave as a rigid panel. Thisis one of the aspects that contribute towards adapting the panel for useas a bearing element an scaffolding. Although the figures in thisdocument are merely schematic figures, which are not drawn to scale,therefore, it may be assumed that the ribs 3 are significantly lessthick than the framework 2. The framework may comprise a few crossconnections, which extend between the two longitudinally extendingplanks or beams. Such a construction of panels is known in the priorart, but within the framework of the present invention such crossconnections may be considered as components of the framework but by nomeans as ribs as referred to in the present invention.

FIGS. 2 a, 2 b and 2 c show a panel, or at least a part thereof, whichis shown in partial view and in exploded view in FIGS. 2 a and 2 b. FIG.2 a shows individual ribs 13, which are already oriented in the mannerin which they are oriented in a panel, however, and the figures showthat the ribs 13 are provided with equally spaced notches 16, via whichthe ribs are interlocked in a fixed orientation with respect to eachother, in which crosswise, interlocked orientation the ribs are spaced afixed distance apart.

FIG. 2 b shows the ribs 13 of FIG. 2 a in an interlocked position. Asthe figure shows, the mating ribs form a grid of squares, and the ribsextend the same distance at the upper side and at the bottom side (notshown), so that a good contact with planar surfaces of the skin plates15 that are to be attached thereto is possible, preferably withoutextending into the skin plates 15 as shown. FIG. 2 c finally shows apanel 11 in which the skin plates 15 and the ribs 13 are glued togetherwith, for at least some embodiments, water repellent glue 17. With thiselement, too, a force that is locally applied to one skin plate 15 willbe distributed over the ribs 13, so that the panel will behave as arigid panel.

The above description and the figures are merely intended by way ofexplanation of the invention and must by no means be construed as beinglimitative to the scope of the invention, which is defined in theappended claims. Alternative embodiments and further aspects arepossible without departing from the scope of the present invention.Panels according to the present invention are suitable for use assubstitutes for, for example, solid wooden planks, for example ifrigidity in the direction perpendicular to the plane of the planks isimportant and/or if the weight of a device in which the panels may beused is an important aspect. The environmental aspects may playa part aswell in the consideration to substitute (solid) planks for panelsaccording to the invention, since less wood is used in the panelsaccording to the present invention than in the case of solid planks, andmoreover lower-grade wood may be used for skin plates than has been thecase so far as a result of the rigidity-enhancing effect of the woodenribs. Possible uses of wooden panels and planks are generally known,which is why such uses of a panel according to the present invention,for example in the construction of scaffolding and in the furnitureindustry, have not been explained as such in the figures and thedescription. The use of panels according to the present invention inscaffolding application is only an example of the various possibleapplications of such panels since one can easily imagine that inscaffolding large forces will be applied on the panels, and thatapplications wherein smaller forces are expected to be applied are thusalso possible.

A density of the product at various thicknesses of one embodiment hasbeen found to be less than 300 kg/m3, such as for a 38 mm thickness, 263kg/m3, a 50 mm thickness 221 kg/m3, a 80 mm thickness 170 kg/m3, and at100 mm thicnness 153 kg/m3. This is on the order of balsa wood withsignificantly higher strength (The density of dry balsa wood ranges from40-340 kg/m3 (2.5-21 lb/ft³), with a typical density of about 160 kg/m³(10 lb/ft³)). Oak is 600-900 kg/m3, yellow pine is 420 kg/m3.Accordingly, the density is less than comparable solid wood alternativestypically used for structural panels.

On the other hand, MDF has a density of 750-800 kg/m3 and MDF typicallyweights 10-15% more (or has that percentage higher density) thanparticleboard of similar dimensions.

Deformation tests were taken of an exemplary embodiment in line with thestandards of EN-310: 1993. Tests were performed at a required span of1.0 m. Additionally, tests were performed using a span of 2.5 m (forcomparison purposes). Results showed structural support for loads of atleast 270 kg (595 lbs). Deflection of the panel at differentthicknesses, is only a few millimeters at most (2.7 mm for a 270 kg loadon the 38 mm embodiment, the deflection being less on the thickerembodiments, namely 50 mm, 80 mm and 100 mm (with it being less than 0.5mm for the 80 and 100 mm embodiments).

The modulus of elasticity was calculated for each of the fourembodiments. For 1 m boards, it ranged from about 3 to about 4.5 GPa,but not exceeding 5 GPa while at 2.5 m it ranged from 1.5 GPa to 4.5GPa. These figures for similar thickness MDF are believed to be aboutthree times higher than MDF (i.e., it deflects three times less thantested MDF under similar loading, MDF is around 1400-3100 N/mm2 forvarious grades). This is also believed to be comparable, but probablyslightly less, than the modulus of elasticity of solid woods like whiteoak, red maple, and pine.

The thinnest product tested with 38 mm thickness when tested at 1 m×1 mpanels has a rupture strength of 600 kg. A modulus of rupture is thus6.62E6. This is lower than many comparable materials (like MDF 14-31N/mm2), but high enough to use for structural applications.

The thickest product of 100 mm was tested and it did not break when 1500kg was applied. A maximum estimated load of 3000 kg is estimated.

The panel of the preferred embodiment is believed to have rigiditycomparable to solid wood products under load, and even improved over MDFwhiles providing a huge weight advantage with an acceptable rupture (orstrength) characteristics.

Prior art panels tested were too flexible to use as structural material,indicating that they had a modulus of elasticity greatly exceeding 5.0GPa.

What is claimed is:
 1. A panel comprising two parallel skin plateshaving perimeters made of a wood material substantially made of MDF,between which ribs extend in a width direction at least substantially awidth between the skin plates for stiffening the panel without extendinginto the skin plates, characterized in that the ribs are at leastsubstantially made of a wood material substantially made of MDF; whereinthe ribs are planar strip-shaped slats and extend orthogonally crosswisefrom one of the two skin plates to but not into the other skin plate,said panel having a density of less than 300 kg/m3 and a modulus ofelasticity not exceeding 5 GPa.
 2. The panel according to claim 1,characterized in that at least some of the ribs extend parallel to eachother in their a longitudinal direction, as defined in a directionperpendicular to the width.
 3. The panel according to claim 2,characterized in that a spacing between two adjacent ribs extendingparallel to each other ranges between 1 and 10 cm, and the panel has upto 70% less wood than the solid wood plank.
 4. The panel according toclaim 2 characterized in that the ribs are arranged in at least one of adiamond-shaped and a rectangular pattern in an interlocking manner withthe ribs extending continuously in at least the longitudinal direction.5. The panel according to claim 4, characterized in that the ribsintersect and are each provided with a respective notch located on eachrib where the ribs intersect with the respective notches engaging oneanother internal to perimeters of the skin plates.
 6. The panelaccording to claim 4, characterized in that the ribs have a thickness,defined in a direction perpendicular to the width, of 0.5 to 2 mm. 7.The panel according to claim 6, characterized in that the ribs have awidth of 20 to 70 mm.
 8. The panel according to claim 7, characterizedin that the ribs are attached to the skin plates.
 9. The panel accordingto claim 8, characterized in that the ribs are adhered to the skinplates.
 10. The panel according to claim 1, characterized in that fibremats are provided between the ribs and the skin plates in contact withthe skin plates and adjacent to the ribs for stiffening purposes and theribs connect directly to the fibre mats.
 11. The panel according toclaim 10, characterized in that said fibre mats are glass fibre mats.12. The panel according to claim 6, characterized in that the skinplates are connected at and around their perimeters to a framework. 13.The panel according to claim 12, characterized in that the framework ismade of wood.
 14. The panel according to claim 12, characterized in thatthe ribs are spaced from the framework.
 15. The panel according to claim1, characterized in that at least a part of the panels iswater-repellent and the ribs connect to the panel with a water repellentglue.
 16. The panel according to claim 14, characterized in that thepanel has a panel length, defined in a direction perpendicular to thewidth, of at least 4 m and a panel width, defined in a directionperpendicular to the width and the panel length, of at least 25 cm.